An enzymatic cycling method is a method in which a concentration of a very small amount of a substance is amplified for measurement by utilizing a function of an enzyme. Conventionally, as a method for measuring a coenzyme, a sensitive measuring method for a coenzyme such as nicotinamide adenine dinucleotide (NAD) cycling using two dehydrogenases is known (see, for example, Non Patent Literature 1). Besides, a cycling method for measuring adenosine triphosphate (ATP) similarly using two kinases has been reported (see, for example, Patent Literature 1). On the other hand, examples of an enzymatic cycling method for measuring not a coenzyme but a substrate include a method for performing measurement by using two transferases and a method for performing measurement by using one enzyme.
An example of the method using two enzymes includes a method using transaminase and polyamine oxidase (see, for example, Patent Literature 2). In this method, putrescine transaminase and polyamine oxidase are used for quantitatively determining putrescine through enzymatic cycling reactions using polyamine oxidase for a reaction from putrescine to 4-aminobutanal and using putrescine transaminase for a reverse reaction, and specifically, hydrogen peroxide produced through the polyamine oxidase reaction is measured by a known coloring method. Similarly, a method for measuring a benzylamine using a benzylamine transaminase and a benzylamine oxidase and a method for measuring tyramine using a benzylamine transaminase and a tyramine oxidase have been reported (see, for example, Patent Literatures 3 and 4).
Besides, as a measuring method employing a cycling method using one enzyme, a method using a dehydrogenase is known (see, for example, Patent Literatures 5 and 6). In this method, an enzymatic cycling reaction utilizing reversible reactivity of a dehydrogenase is caused to proceed in the presence of oxidized coenzyme NAD (P) or an analog thereof, and a reduced coenzyme NAD (P) or an analog thereof, so as to sensitively quantitatively determine a substrate for the dehydrogenase, and this method is applied to quantitative determination of bile acid using 3α-hydroxysteroid dehydrogenase in the presence of thio-NAD and reduced NAD, or quantitative determination of glucose-6-phosphate using glucose-6-phosphate dehydrogenase, for example.
Conventionally, as a measuring method for a substrate as a measurement target using a kinase, for example, a method for measuring triglyceride is known (see, for example, Non Patent Literature 2). Besides, a method for measuring creatinine is known (see, for example, Patent Literature 7). In this measuring method, creatinine is converted into creatine by a function of creatinine amidohydrolase, the creatine is further converted, in the presence of ATP, into creatine phosphate and adenosine diphosphate (ADP) by creatine kinase, then the ADP is measured for measuring the creatinine.